What is this?

Yup and you need to bypass it before it gives trouble. First couple of years of the dreaded "seatbelt buzzer" system, it was interlocked so you had to have them fastened to run the car. That thing has a reset button in case of trouble. Look on the plug. There will be a yellow and yellow / tracer wires and this thing "breaks" that path on the way to the starter relay.

Figure a way to permanently connect the two yellows together

Here:

http://www.forabodiesonly.com/mopar/showthread.php?p=1969624169

http://www.forabodiesonly.com/mopar/showthread.php?t=14304